1. Field of the Invention
The present invention relates to high-frequency composite parts used in a high-frequency circuit section of a portable telephone of a personal handy-phone system (PHS) type or a personal digital cellular (PDC) type.
2. Description of the Related Art
FIG. 10 and FIG. 11 are block diagrams of known PHS portable telephones. In a PHS portable telephone shown in FIG. 10, when transmitting, a signal to be transmitted is converted to an RF signal, passes through a filter F1 in a transmission circuit (Tx), is amplified by an amplifier AMP1 in the Tx side, passes through a high-frequency switch SW and a top filter F2, and is transmitted from an antenna ANT. On the other hand, when receiving, a signal is received from the antenna ANT, passes through the top filter F2, passes through the switch SW, and is amplified by an amplifier AMP2 in a receiving circuit (Rx). Then, signals in frequency bands other than that of the signal to be received are removed by a filter F3 in the Rx side.
In a PHS portable telephone shown in FIG. 11, when transmitting, a signal to be transmitted is converted to an RF signal, passes through a filter F1 in the Tx side, is amplified by an amplifier AMP1 in the Tx side, passes through a second filter F4 in the Tx side and a high-frequency switch SW, and is transmitted from an antenna ANT. On the other hand, when receiving, a signal received from the antenna ANT passes through the switch SW, and is amplified by an amplifier AMP2 in a receiving circuit (Rx). Then, signals in frequency bands other than that of the signal to be received are removed by a filter F3 in the Rx side.
These PHS portable telephones have been made compact and lightweight by highly dense mounting of compact, surface-mounting, high-frequency parts, such as the parts in FIGS. 10 and 11, on a printed circuit board.
It is expected that portable telephones will be made more compact and lightweight in the future while having more advanced functions. Therefore, high-frequency parts to be mounted on a board, such as those mentioned above, need to be made further compact and lightweight.
In a conventional portable telephone, however, since a discrete high-frequency switch and a discrete amplifier are mounted on a printed circuit board, it is difficult to make the telephone more compact and lightweight. Another restriction in the design phase of the conventional portable telephone is that characteristic-impedance matching is required for each of the high-frequency switch and the amplifier, which requires a matching circuit.